Interestingly, while all of the HIV-1 DNA produced during the spreading infection mounted by IN− HIV-1 in the presence of Tax was, as expected, unintegrated (Fig. 3A and F), much of this DNA is in the form of HIV-1 DNA circles, with 2LTR circles contributing ∼30% of the total (Fig. 3E and F). Here, CNTN2 is linked to infection.